With demands for lightening, miniaturizing and densification, substitution of optically transparent resins for inorganic glasses has been advanced recently in fields of optical parts, such as lenses and sealing materials, and liquid crystal display element parts, such as back lights, light guide plates, substrates for TFT and touch panels, where inorganic glasses have been heretofore employed. As the optically transparent resins, addition polymers of norbornene (bicyclo[2.2.1]hept-2-ene) type having features of high transparency, high heat resistance and low water absorption properties have been paid attention.
Further, as transparent resins having, in addition to the above features, small coefficient of linear expansion, excellent thermal dimensional stability, excellent chemical resistance and excellent adhesion to other materials, addition polymers of norbornene (bicyclo[2.2.1]hept-2-ene) and cycloolefins having a hydrolyzable silyl group and their crosslinked products have been proposed (see patent document 1).
Addition polymers of cycloolefins such as norbornene have been obtained by addition polymerization of cycloolefin monomers by the use of catalysts using compounds of transition metals such as Ni, Pd, Ti, Zr and Cr (see, e.g., non-patent document 1)
Addition copolymers of cycloolefin compounds having a polar substituent in the side chain and non-polar cycloolefin compounds are useful as copolymers not only having excellent heat resistance and transparency but also being capable of crosslinking to improve adhesion properties, dimensional stability and chemical resistance, and as polymerization catalysts for obtaining these copolymers, single complexes of late transition metals, such as Ni and Pd, or multi-component catalysts containing Ni or Pd compounds have been mainly employed (see patent documents 1 and 2, non-patent documents 2 to 11).
Of these catalysts, the multi-component catalysts are industrially employed more frequently rather than the single-component catalysts, in order to omit a complicated catalyst synthesis process.
As catalysts of excellent polymerization activity, those using a phosphine compound or an amine compound as a Pd cation ligand and as a neutral donor and using a superstrong acid anion as a weak counter anion ligand are known (see patent documents 1 and 3 to 6, non-patent document 12).
Such multi-component catalysts as used in the prior art are obtained by preparing any of the following catalyst systems.
Catalyst System I
(1) Pd compound
(2) Neutral phosphine or amine compound
(3) Ionic compound capable of becoming weak counter anion for Pd cation
(4) Organoaluminum compound
Catalyst System II
(1) Pd compound having neutral phosphine or amine compound as ligand
(2) Ionic compound capable of becoming weak counter anion for Pd cation
(3) Organoaluminum compound
Catalyst System III
(1) Pd compound having, as ligand, neutral donor having Pd—C bond, such as σ-alkyl, σ-aryl or π-allyl
(2) Ionic compound capable of becoming weak counter anion for Pd cation
Catalyst System IV
(1) Pd compound having, as ligand, neutral donor having Pd—C bond, such as σ-alkyl, σ-aryl or π-allyl
(2) Lewis acid compound
In any of the above catalysts, a phosphine or amine compound as a neutral donor is contained. In case of Pd compounds having, as a ligand, a neutral donor and having Pd—C bond, such as σ-alkyl, σ-aryl or π-allyl, however, syntheses of their complexes become complicated, so that it cannot be necessarily said that they are industrially advantageous. In the prior art, any catalyst having as its constituent an ionic phosphonium salt instead of such a neutral donor has not been known heretofore.
In the case where polymerization of 5-trialkoxysilylbicyclo[2.2.1]hept-2-ene having a hydrolyzable silyl group and bicylo[2.2.1]hept-2-ene (norbornene) having no substituent in the side chain is carried out in a hydrocarbon solvent using a conventional neutral donor catalyst system, a polymer having a compositional distribution is liable to be produced, or precipitation sometimes take place during the polymerization, or the resulting polymer sometimes becomes opaque. It is thought that this is caused by that reactivity of the 5-trialkoxysilylbicyclo[2.2.1]hept-2-ene is higher than that of the bicylo[2.2.1]hept-2-ene, so that the 5-trialkoxysilylbicyclo[2.2.1]hept-2-ene is polymerized in a larger ratio compared to a ratio of these charged monomers at the stage of the beginning of the polymerization, and as a result, a polymer having structural units derived from the 5-trialkoxysilylbicyclo[2.2.1]hept-2-ene in a higher proportion is formed, that is, a compositional distribution regarding the structural units of the polymer occurs, and consequently, solubility in the polymerization solvent or compatibility with the polymer formed in the latter half of the polymerization reaction is lowered.
Moreover, if a compositional distribution regarding the structural units derived from the 5-trialkoxysilylbicyclo[2.2.1]hept-2-ene occurs, crosslink network of a crosslinked product obtained by crosslinking the polymer utilizing the hydrolyzable siyl group becomes ununiform, and the crosslinked product sometimes has poor dimensional stability.
Therefore, as a polymerization process substantially bringing about no compositional distribution, a process wherein one of the monomers is continuously or successively added to the polymerization system can be considered. However, it is thought that such a control becomes difficult if a reactivity ratio of the monomer copolymerized greatly differs.
As a means to prevent precipitation even if such a compositional distribution occurs, copolymerization of the 5-trialkoxysilylbicyclo[2.2.1]hept-2-ene and a cycloolefin compound having an alkyl group of 3 or more carbon atoms as a side chain substituent can be considered. In this case, however, when a film or a sheet is formed from the resulting copolymer, the film or the sheet has a too large coefficient of liner expansion though it has flexibility, and a problem of dimensional stability sometimes takes place. In this case, further, the compositional distribution sometimes becomes much larger, and therefore, a problem of transparency of the resulting polymer and a problem of uniformity of a crosslink network of a crosslinked product formed from the polymer is liable to take place.
In the polymerization reaction of a cycloolefin compound having an ester group or an oxetane group with the bicylo[2.2.1]hept-2-ene, reactivity of the cycloolefin compound having an ester group or an oxetane group is lower than that of the bicylo[2.2.1]hept-2-ene differently from the case of using the aforesaid cycloolefin compound having a hydrolyzable silyl group, so that a polymer having structural units derived from the cycloolefin compound having an ester group or an oxetane group in a lower proportion is formed at the stage of the beginning of the polymerization. With regard to occurrence of a compositional distribution, however, this polymerization is similar to that using the cycloolefin compound having a hydrolyzable silyl group, and the same problems sometimes take place.
On this account, there has been desired a catalyst system which does not substantially bring about the aforesaid compositional distribution in the polymerization reaction of a cycloolefin compound having a polar substituent such as a hydrolyzable silyl group, an ester group or an oxetane group with a non-polar cycloolefin compound and therefore which does not cause precipitation or turbidity of the resulting polymer during the polymerization using a hydrocarbon solvent.
Further, the Pd catalyst is expensive, and remaining of a large amount of the Pd catalyst in the polymer causes coloring or a lowering of transparency of the polymer, and accordingly, there has been desired a catalyst capable of performing polymerization in a small catalytic amount and showing high polymerization activity.
Furthermore, although the multi-component catalyst containing the Pd compound has higher resistance to water or methanol than the multi-component catalyst containing a compound of an early transition metal of Ti or Zr, phosphine that is added as a neutral donor to improve polymerization activity is liable to be oxidized and becomes phosphine oxide if oxygen is present when it is stored, and as a result, lowering of polymerization activity is sometimes brought about. Especially in the polymerization with a small catalytic amount, the catalyst becomes different even in the presence of a trace amount of oxygen, and the influence of oxygen is great.
On this account, a catalyst system which brings about little variability in the polymerization rate and the quality of the resulting polymer even in the presence of a trace amount of oxygen in the polymerization system has been desired from the viewpoint of industrial production.
Moreover, production of a cycloolefin addition polymer crosslinked product having adhesion properties or solvent resistance and chemical resistance usually includes a step of producing a copolymer that is a precursor of the crosslinked product by performing addition polymerization reaction of a cycloolefin compound having a polar substituent that becomes a crosslinking group, such as a hydrolyzable silyl group or an ester group, with a non-polar cycloolefin compound. From the copolymer formed by such an addition polymerization reaction, however, removal of palladium atom is difficult in many cases, and a large amount of residual palladium in the resulting copolymer causes a problem of lowering of optical transparency.
Patent document 1: U.S. Pat. No. 6,455,650
Patent document 2: U.S. Pat. No. 3,330,815
Patent document 3: Japanese Patent Laid-Open Publication No. 262821/1993
Patent document 4: WO 00/20472
Patent document 5: Japanese Patent Laid-Open Publication No. 130323/1998
Patent document 6: Japanese Patent Laid-Open Publication No. 98035/2001
Non-patent document 1: Christoph Janiak, Paul G. Lassahn, Macromol. Rapid Commun. 22, p. 479 (2001)
Non-patent document 2: R. G. Schultz, Polym. Lett. Vol. 4, p. 541 (1966)
Non-patent document 3: Stefan Breunig, Wilhelm Risse, Makromol. Chem. 193, 2915 (1992)
Non-patent document 4: Adam L. Safir, Bruce M. Novak Macromolecules, 28, 5396 (1995)
Non-patent document 5: Joice P. Mathew et al., Macromolecules, 29, 2755-2763 (1996)
Non-patent document 6: Annette Reinmuth et al., Macromol. Rapid Commun. 17 173-180 (1996)
Non-patent document 7: B. S. Heinz, Acta Polymer 48, 385 (1997)
Non-patent document 8: B. S. Heinz et al., Macromol. Rapid Commun. 19, 251 (1998)
Non-patent document 9: Nicole R. Grove et al., J. Polym. Sci. Part B, 37, 3003 (1999)
Non-patent document 10: April D. Hennis et al., organometallics, 20, 2802 (2001)
Non-patent document 11: Seung U K Son et al., J. Polym. Sci. Part A, Polym. Chem. 41, 76 (2003)
Non-patent document 12: John Lipian et al., Macromolecules, 35, 8969-8977 (2002)
The present invention has been made under such circumstances as described above, and it is an object of the present invention to provide a process for producing a cycloolefin addition polymer in which one or more cycloolefin monomers can be addition-(co)polymerized with a small amount of a palladium catalyst and a cycloolefin (co)polymer can be produced with high activity.
It is another object of the present invention to provide a process for producing a cycloolefin addition polymer using a catalyst of high polymerization activity, in which when a monomer composition comprising a specific cycloolefin compound and a cycloolefin compound having a polar substituent such as a hydrolyzable silyl group is polymerized, a compositional distribution regarding structural units derived from the cycloolefin compound having a polar substituent is not substantially brought about.
It is a further object of the present invention to provide a process for producing a cycloolefin addition polymer using a novel catalyst whose polymerization activity is little influenced even when a trace amount of oxygen is present in the (co)polymerization reaction of cycloolefin compounds and which is capable of carrying out addition (co)polymerization with high activity even when monomers containing a cycloolefin compound having a polar substituent such as a hydrolyzable silyl group are (co) polymerized.